The invention relates to a lighter-than-air aerostat, of the type comprising at least one main chamber closed in a sealed manner, with a constant volume, which is pressurised by a gas lighter than air, such as to permit rising and flight of the aerostat. Throughout the present application, xe2x80x9caerostatxe2x80x9d means any vehicle lighter than air, and xe2x80x9cgeostationaryxe2x80x9d means the fact that an aerostat remains at least substantially vertical relative to a point which is fixed in relation to the ground.
So-called free aerostats are those which are not connected mechanically to the ground, unlike captive aerostats. Conventional free balloons have the disadvantage that they drift, in particular horizontally, in relation to the ground, according to the winds, without any possibility of controlling their position or their path. Captive balloons do not have this disadvantage, and are at least substantially geostationary. However, they require at least one cable for connection to the ground, which is heavy and triangulated, is a source of danger for air traffic, and in practice prevents selection of this technology for aerostats which are designed to fly at a high altitude, and in particular for stratospheric aerostats.
If it is required to be able to pilot the horizontal position (i.e. the position relative to the ground) and/or the horizontal path of a free aerostat for a long period of time (ranging from a few months to several years), it is out of the question to have on board consumable energy. With solar energy, the problem must be faced of the weight of the collector devices and of the means of storage, taking into account firstly the fact that the efficiency of the electric motors (in particular the ratio of the thrust to the power consumed) is too low, and secondly the night flight which must be assured.
In addition, since free aerostats are extremely sensitive to meterological conditions and horizontal winds, a very large inflated volume must be provided, in order to be able to carry on-board position-correction motors, the power of which makes it possible to compensate for the horizontal aerodynamic drag.
In particular, it is known that a stratospheric geostationary balloon would require a minimum volume of approximately 350,000 m3, and a minimum weight of approximately 10 tonnes, in order to be able to carry motors making it possible to control its horizontal position and/or its horizontal path at a stratospheric altitude, as well as a useful load such as a telecommunications system. Dimensions of this type represent a substantial volume, and a significant risk for air traffic, and for the populations, if the balloon falls or is destroyed. In addition, these dimensions cause problems of practical production and launching. In addition, the assembly would have a high cost, for relatively low reliability.
However, long-lasting stratospheric missions would permit scientific study of the upper atmosphere, observation of the earth, improvement of telecommunications, etc. In particular, it is desirable to be able to have at a stratospheric altitude numerous devices which can act as active or passive relays for hertzian connections, for example for telecommunications satellites (mobile telephony, radio, television, data networks, etc) or localisation satellites (GPS, Argos systems, etc).
Therefore, there is a need to be able to place vehicles at a high atmospheric altitude, and in particular at a stratospheric altitude, the position or displacements of which relative to the ground, in particular horizontally, can be controlled automatically or from the ground, without a human pilot on board, for a duration which can be between a few days and several years.
The object of the invention is thus to eliminate these disadvantages, by providing a free vehicle which is designed for a high atmospheric altitude, and in particular a stratospheric altitude, and of which the horizontal position (in longitude and latitude) and/or the horizontal displacements relative to the ground can be controlled automatically, autonomously or from the ground, for a substantial period of time.
In particular, the object of the invention is to solve the problem posed by the energy necessary for motorisation, which makes it possible to maintain the horizontal position and/or to follow a horizontal path.
More particularly, the object of the invention is to provide a vehicle of this type, formed from an aerostat which is designed for a high atmospheric altitude, and in particular a stratospheric altitude, the volume of which is limited, and in particular is between 10 m3 and 10,000 m3, for example approximately 2,000 m3, for a weight of between 10 kg and 500 kg, and in particular between approximately 50 kg and 200 kg.
In addition, the object of the invention is to provide an aerostat which is particularly suitable for acting as an active and/or passive relay for transmission of data by hertzian means, in particular in the field of hyperfrequencies.
For this purpose, the invention relates to a lighter-than-air aerostat, comprising:
a strengthening structure, which defines a shape which is symmetrical relative to a main axis;
at least one main chamber closed in a sealed manner, which is integral with the said structure, and is pressurised by a gas which is lighter than air, such as to permit flight of the aerostat;
means for driving the aerostat comprising:
one or a plurality of particle-emission propulsion units supported by the said structure, which are regularly distributed around the main axis, and are designed to be able to drive the aerostat in rotation in one direction around the main axis, and to be able to be controlled from an active state to an inactive state and vice-versa, at least once for each rotation of the aerostat around the main axis;
one or a plurality of mobile flaps, which are supported by the said structure outside the main chamber, are distributed regularly around the main axis, and are designed to be able to be controlled at least once for each rotation of the aerostat around the main axis, from an active state, in which they brake the rotation of the aerostat, whilst exerting aerodynamic thrust which tends to displace the aerostat in translation perpendicularly relative to the main axis, to an inactive state, in which they do not offer any substantial resistance to the rotation of the aerostat, and vice versa; and
on-board control means, which are designed to control the propulsion units and the flaps in order to
drive the aerostat in continuous rotation around the main axis; and
drive the aerostat in translation, with at least one component which is perpendicular to the main axis, relative to the volume of air in which it moves.
xe2x80x9cTranslation with at least one component perpendicular to the main axisxe2x80x9d means movement of translation in a direction of translation which has a component which is non-zero, according to the direction which is radial relative to the main axis, i.e. which is not parallel to the main axis. Preferably, advantageously and according to the invention, the means for driving the aerostat are designed to drive the aerostat in translation in a direction of translation which is at least substantially radial relative to the main axis, i.e. which is perpendicular to the main axis.
Advantageously, an aerostat according to the invention has an overall axial dimension parallel to the main axis which is smaller than that of its overall radial dimension perpendicular to the main axis. Preferably, and according to the invention, it has a general outer shape which is globally symmetrical in revolution around the main axis, and in particular is globally lenticular.
In one embodiment, and according to the invention, the aerostat has an overall radius of between 5 m and 50 m, and in particular approximately 15 m, and an overall axial height of between 1 m and 20 m, and in particular approximately 10 m.
Advantageously and according to the invention, the aerostat comprises at least one ionic actuator and/or at least one air pulsation unit, as a particle-emission propulsion unit, these particles then being respectively ions and/or gas molecules.
Advantageously and according to the invention, each of the propulsion units is associated with a peripheral portion of the said strengthening structure which is furthest away from the main axis, and is disposed such as to exert a drive force which is at least substantially tangential. Similarly, advantageously and according to the invention, each of the flaps is associated with a peripheral portion of the said structure which is furthest away from the main axis, and is disposed such as to exert a force which is at least substantially tangential.
Advantageously and according to the invention, each mobile flap extends at least substantially radially, and is mobile parallel to the main axis, between a position retracted in a flap compartment, in which it does not interfere with the relative current of air obtained from the displacements of the aerostat relative to the volume of air in which the aerostat is placed, and an extended position, in which it interferes with the current of air, and tends to brake the rotation of the aerostat around the main axis, whilst exerting reactive aerodynamic thrust, which drives the aerostat in translation.
In addition, advantageously and according to the invention, the on-board control means are designed such that, in a first angular sector, which extends from one side in a radial direction which is perpendicular to the main axis, and fixed in relation to the corresponding wind (independently of the rotation of the aerostat around the main axis), each propulsion unit is in the active state, and each flap is in the inactive state, whereas in a second angular sector, which extends to the other side of this radial direction, each propulsion unit is in the inactive state, and each flap is in the active state, such that the aerostat is driven in translation relative to the corresponding wind, at least substantially according to this radial direction. Preferably and according to the invention, the drive means are designed to be able to drive the aerostat in rotation around the main axis at a speed xcfx89 which is at least substantially constant, of between 1 rd/s and 100 rd/s, and in particular approximately 2xcfx80 rd/s. In addition, advantageously according to the invention, each propulsion unit and each flap is designed to be able to be controlled from the inactive state to the active state, and from the active state to the inactive state, in a period of less than 2xcfx80/4xcfx89, xcfx89 being the speed of rotation of the aerostat expressed in radians per second.
Advantageously, an aerostat according to the invention additionally comprises means for location of the position of the main axis relative to a reference point which is fixed in relation to the ground, and means for location relative to this same fixed reference point for the angular position (in rotation) of the structure relative to the main axis, and the said control means comprise calculation means which are designed to determine the control signals to be applied to each propulsion unit and to each flap, according to signals emitted by these location means, and in accordance with a predetermined instruction signal for the horizontal position and/or the horizontal path of the main axis, relative to the fixed reference point.
Advantageously, the aerostat according to the invention is characterised in that it comprises at least one flexible outer envelope, which delimits at least one main chamber which is sealed against gases, and is pressurised by a gas lighter than air, and in that each of the mobile flaps is disposed outside this outer envelope. Similarly, each propulsion unit is secured to the structure inside the envelope, and has a particle-ejection nozzle, which passes through the envelope in a sealed manner, in order to emit the particles outside the envelope.
Advantageously and according to the invention, the gas consists of helium, and the volume of the main chamber is designed to permit stratospheric flight of the aerostat.
Advantageously and according to the invention, the aerostat is additionally characterised in that the structure comprises a peripheral toric balloon, which is sealed against gases, and is over-pressured by a gas lighter than air, to a pressure greater than that of the main chamber, in that it comprises the same number of propulsion units as flaps, and in that it comprises support parts which are secured to this balloon, and are regularly distributed around the main axis, each support part supporting at least one propulsion unit and/or at least one mobile flap.
In one embodiment, and according to the invention, the structure comprises:
a rigid, globally cylindrical hollow/central core, which can enclose the electronic and/or computer and/or telecommunications and/or energy storage equipment, and/or equipment of an on-board mission;
an over-pressurised peripheral toric balloon;
support parts which are secured to the peripheral toric balloon, and support the propulsion unit(s) and the mobile flap(s);
connection means, which connect the central core and the support parts; and
an outer envelope, which surrounds and/or completes the volume delimited by the peripheral toric balloon and the central core, in order to circumscribe at least one pressurised, sealed main chamber.
In addition, an aerostat according to the invention comprises an on-board energy source, which is designed to assure the energy supply at least of each propulsion unit. Preferably and according to the invention, this energy source is also designed to assure the energy supply of drive units for manoeuvring the flaps, as well as the energy supply of the control means, the location means, and the on-board mission, i.e. of the aerostat as a whole, which is then totally autonomous from the point of view of its energy supply.
Advantageously and according to the invention, the energy source comprises:
photovoltaic solar cells which are disposed on at least one upper surface portion of the aerostat; and
means for storage of electrical energy.
The electrical energy storage means can consist of rechargeable accumulators and/or a fuel cell/fuel cells. Their capacity is determined such as to permit night flight.
The invention thus makes it possible to obtain a free aerostat which can be launched to a high altitude, and in particular to a stratospheric altitude, and of which the horizontal position and/or the horizontal path can be controlled automatically for a long period of time. In particular, it should be noted that the drive means for the aerostat make it possible to use for displacement in horizontal translation of the aerostat, most of the kinetic energy of the particles emitted by the propulsion units, which are themselves displaced relative to the volume of air (by the rotation of the aerostat) at a speed which is very much higher than the speed of horizontal translation of the aerostat. The propulsion power created by each propulsion unit is greatly increased compared with the case of an aerostat which is not driven in continuous rotation. For the same resulting force of propulsion in horizontal translation, the invention makes it possible to reduce considerably the energy consumption, and thus the weight of the energy source (solar cells, storage cells, etc), which is a determining factor within the context of production of a long-lasting free aerostat, which is geostationary, or mobile according to a predetermined path.
The invention also relates to an aerostat which is characterised in association by some or all of the characteristics described previously or hereinafter.